Field trials have showed that genetically modified (GM) rice yields higher output, lowers pesticide use, and thus reduces pesticide-related health problems, researchers from China and the United States said on Thursday.

The joint study, whose results will be published in the April 29 issue of the journal Science, was conducted by Huang Jikun and Hu Ruifa at the Chinese Academy of Sciences; Scott Rozelle at the University of California, Davis; and Carl Pray at Rutgers University.

"This paper studies two of the four GM varieties that are now in farm-level pre-production trials, the last step before commercialization," said co-author Pray.

"Farm surveys of randomly selected farm households that are cultivating the insect-resistant GM rice varieties demonstrate that when compared with households cultivating non-GM rice, small and poor farm households benefit from adopting GM rice by both higher crop yields and reduced use of pesticides, which also contributes to the improved health of farmers."

China began research on genetically modified agricultural crops in the 1980s, but has not yet developed any GM food crops for the commercial market.

The researchers conducted an economic analysis of data from eight rice field trials in China. Their goal was to determine whether GM rice was helping farmers reduce pesticide use in the fields, increasing yield and having any identifiable health effects on the farmers growing the genetically modified rice strains.

The field trials involved two GM rice strains: the Xianyou 63, created to be resistant to rice stem borer and leaf roller; and the Youming 86 variety, which is insect-resistant due to the introduction of a resistance gene from the cowpea plant. Both varieties have been in pre-production field trials since 2001.

These field trials were designed to identify the effects of the GM crops on farm households before the crops are commercialized.

Data from surveys revealed that the characteristics of the farm households were nearly identical, regardless of what type of rice they were growing. The main difference between the farm households was in the level of pesticides they used.

The study showed that the quantity and cost of pesticides applied to the conventional rice was 8 to 10 times as high as that applied to the insect-resistant GM rice.

The survey data also showed that there was a difference in yields between the GM and non-GM rice varieties.

Yields of the GM Xianyou 63 variety were 9 percent higher than those of conventional rice varieties. However, yields of the GM Youming 86 were not significantly different from those of conventional varieties.

Because there is a high incidence of pesticide-related illness in households of developing countries, the researchers were interested in tracking the health effects of the insect-resistant GM rice.

The surveys indicated that none of the farmers who had completely planted their farms to the GM insect-resistant rice varieties reported experiencing adverse health effects from pesticide use in either 2002 or 2003.

Among farmers growing plots of the GM rice and plots of conventional rice varieties, 7.7 percent reported pesticide-induced illness incidents in 2002, and 10.9 percent reported such cases in 2003. None of those households reported being affected after working on plots with the GM varieties.

"This study provides evidence that there are positive impacts of the insect-resistant GM rice on productivity and farmer health," the researchers concluded.